The present invention relates to a method and system for media authentication and, more particularly, to a method and system for authenticating digital optical media.
Digital optical media includes, but is not limited to, media such as Compact Disc (CD), Compact Disc Read-Only Memory (CD-ROM), and Digital Video Disc (DVD). Digital optical media are well-known in the art and have become the media of choice for a broad variety of important data storage and information distribution applications. In particular, certain proprietary materials such as computer software, specialized data, and audio/video content are commonly sold and distributed on digital optical media.
Digital optical media technology is established according to a series of international publications, herein referred to as "standards", all of which are incorporated herein by reference as if set forth fully herein. For example, some common standards applicable to CD's include: the International Standards Organization (ISO) standard 9660 entitled "Information Processing--Volume and File Structure of CD-ROM for Information Interchange, ISO Standard 13490-1", the International Electrotechnique Commission (CEI-IEC) standard 908, generally conforming to what is known as the "Red Book", and ISO/IEC 10140, generally conforming to what is known as the "Yellow Book".
Software and document data may be read and utilized by a computer from digital optical media, and there are widely-available players for reading data from digital optical media and using this data to reconstruct audio, visual, text, and audio-visual information. The term "player" herein denotes any device which is able to read data from digital optical media. Players include, but are not limited to, CD players, CD-ROM multi-media players, game-playing systems, and DVD players, which can reproduce sound, images, and text from data stored on digital optical media. Some computers are also configured with hardware and software capable of accessing digital optical media, to duplicate the functionality of CD players, CD-ROM multi-media players, game-playing systems, and DVD players.
Unfortunately, it is easy to copy proprietary material from an original digital optical medium and thereby produce an unauthorized copy whose sale and distribution cannot be controlled by the owner of the proprietary material. Individual users can freely copy such proprietary material using low-cost consumer devices such as CD-R recorders, and it is also possible to mass-produce unauthorized copies of proprietary material using commercial mastering equipment. It is usually difficult or impossible to enforce copyright laws in such cases, and the legitimate owner of the proprietary material is thereby deprived of the legal right to control the sale and distribution of the proprietary material. The term "original" as used herein refers to an instance of a digital optical medium which has been authorized by and issued under the control of the owner of the proprietary material recorded thereon. In contrast, the term "unauthorized copy" herein denotes an instance of a digital optical medium which has derived from an original digital optical medium via copying that has neither been authorized by nor is under control of the owner of the proprietary material recorded thereon.
Thus, there is a widely-recognized need for a means of distinguishing an original digital optical medium from an unauthorized copy, and especially, there is a widely-recognized need for a means of automatically distinguishing an original digital optical medium from an unauthorized copy. The term "automatically distinguish" herein denotes a means of distinguishing an original digital optical medium from an unauthorized copy in such a way that does not require visual inspection or other human intervention. In particular, automatically distinguishing an original digital optical medium from an unauthorized copy should be feasible by a player as it reads the digital optical medium. That is, whatever distinguishing features are placed on an original digital optical medium for identification as original, the distinguishing features must be machine-readable. The terms "authenticate" and "authenticating" herein refer to any process by which an undetermined digital optical medium corresponding to an original digital optical medium can be differentiated to be an original digital optical medium as distinct from an unauthorized copy of an original digital optical medium. The term "undetermined" herein denotes that a specific instance of a digital optical medium is not yet known to be an original digital optical medium as distinct from an unauthorized copy. The term "corresponding to" herein denotes that a specific instance of a digital optical medium contains the same functional data as a given original digital optical medium.
In addition to allowing a player to identify the digital optical medium being played as an original rather than an unauthorized copy, a method for authenticating an undetermined digital optical medium can allow the player to selectively access proprietary material only if the digital optical medium is an original, and deny access to the proprietary material if the digital optical medium is an unauthorized copy. Such selective access is a means of copy protection, and can be implemented through various techniques known in the art, such as by encrypting the proprietary material and storing a decryption key on the original digital optical medium in such a way that the decryption key is not readily copyable. The presence of a valid decryption key on a digital optical medium therefore is intended to automatically distinguish the digital optical medium as original, and moreover to provide copy protection by allowing the player access to the proprietary material only if the digital optical medium is original. The term "copy protection" herein denotes any method or system which either prevents the making of an unauthorized copy or renders an unauthorized copy useless for its intended application.
There are currently a number of schemes which attempt to automatically distinguish an original digital optical medium from an unauthorized copy by storing a special pattern, such as a decryption key, on the digital optical medium in such a way that the special pattern is not readily copyable. For example, U.S. Pat. No. 5,400,319 to Fite et al. ("CD-ROM with Machine-Readable I.D. Code") discloses the use of a laser to selectively destroy portions of the reflective layer of the CD-ROM, thereby creating addressable defects in which a serial number may be encoded. U.S. Pat. No. 5,563,947 to Kikinis ("CD-PROM") discloses a similar use of a laser to physically damage selected sectors and thereby produce a pattern of unreadable sectors in which a decryption key may be stored. And U.S. Pat. No. 5,703,858 to Mitchell et al. ("System for Encoding a Glass Master to Enable Detection of a Counterfeit Optical CD-ROM") discloses the use of a high-frequency random modulation of a laser to produce random defects in the CD-ROM at the master level by selective destruction of redetermined sectors. All of these techniques, as well as other currently-available commercial techniques for copy-protecting digital optical media, involve creating damaged, invalid, or otherwise unreadable portions of the digital optical medium. The theory behind such techniques is that ordinary consumer recording equipment is not intended to be able to produce defects in the copies and therefore an unauthorized copy produced on such equipment should lack the unreadable areas in which the decryption key or other pattern is encoded. If this were in fact reliably the case, then such techniques would provide means for authenticating an undetermined digital optical medium. The present applicants, however, have found that it is possible to reproduce unreadable sectors in a copy by using ordinary consumer recording equipment with the appropriate software. Thus, a person with access to the proper software would be able to easily defeat such schemes relying on unreadable sectors and thereby create an unauthorized copy of a digital optical medium which will be incorrectly discerned by these authenticating schemes to be an original digital optical medium. In effect, all the schemes currently known in the art for providing copy protection of digital optical media by encoding patterns in damaged or unreadable data areas are of limited value in distinguishing an original digital optical medium from an unauthorized copy and offer only limited protection against making unauthorized copies.
Therefore, it would be highly advantageous to have a method and system for authenticating an undetermined digital optical medium which cannot be defeated utilizing commercially-available copying equipment, regardless of the software employed. This goal is met by the present invention.